Sofa beds, convertible sleepers, seat beds and other foldable bed or seat units suffer from the fact that their mattresses are necessarily limited in depth to say, for example, a maximum of two and three-quarter inches (23/4") for tri-fold beds and four inches (4") for standard sleepers. This drawback is caused by the requirement of the mattress to fold into the limited confines of the frame which is typically designed to provide low seat height requirements which therefore place a definite limitation on the size of the mattress depth.
The result is that the mattress, when unfolded to be used as a body support for sleep, does not provide the needed comfort and support to the body. On the contrary, the mattress is uncomfortable to the sleeper and also tends to hammock through use thereby increasing the discomfort while shortening the life of the mattress.
The aforementioned problem also has placed a limitation on the styling of sofa beds or convertible sleepers or seat beds so that it has been heretofore difficult if not impossible, to provide a low seat style in keeping with present-day tastes and at the same time, a mattress of sufficient depth to provide the necessary comfort and support to the user.